Multifocal contact lens

ABSTRACT

A multifocal contact lens customized for a patient has, in accordance with the present invention, an anterior side with a power curve defined in part by a (i) central aspheric surface, (ii) an inner annular surface contiguous with the central aspheric surface, (iii) a second annular surface contiguous along a radially inner periphery with the inner annular aspheric surface, and (iv) an outer annular surface contiguous along a radially inner periphery with the second annular aspheric surface. Each of the annular surfaces is concentric or coaxial with the central aspheric surface. The central aspheric surface corresponds to a distance vision correction zone. The inner annular surface is an aspheric surface corresponding to a progressive add zone with a standard eccentricity between approximately -1.5 and approximately -5.0. The second annular surface corresponds to a near vision correction zone, and the outer annular surface corresponds to a distant vision correction zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.08/040,422 filed Mar. 31, 1993, now U.S. Pat. No. 5,404,183 applicationSer. No. 08/111,845, filed Aug. 25, 1993, now U.S. Pat. No. 5,493,350and application Ser. No. 08/201,699 filed Feb. 25, 1994 now U.S. Pat.No. 5,526,071. Application Ser. No. 08/111,845 now U.S. Pat. No.5,493,350 is a continuation-in-part of application Ser. No. 08/040,422,now U.S. Pat. No. 5,404,183 while application Ser. No. 08/201,699 nowU.S. Pat. No. 5,526,071 is a continuation-in-part of application Ser.No. 08/040,422 now U.S. Pat. No. 5,404,183 and application Ser. No.08/111,845 now U.S. Pat. No. 5,493,350.

BACKGROUND OF THE INVENTION

This invention relates to a multifocal hydrophilic ("soft") and methodof use in preparing and fitting a customized multifocal contact lens.This invention also relates to a multifocal contact lens produced usingsuch a method.

Bifocal contact lenses are designed to correct or compensate for acondition of advancing age known as "presbyopia." In a presbyopic eye,the ability to focus at near distances, such as the normal readingdistance, and in some cases at intermediate distances, is diminished.The loss of focusing capability is due to hardening of the eye's naturalcrystalline lens material.

Generally, multifocal contact lenses (usually either bifocal, trifocalor aspheric) are concentric or segmented in configuration. In aconventional bifocal contact lens of the concentric type, a first,centrally located, circular correction zone constitutes either distantor near vision correction, while a second annular correction zonesurrounding the first zone provides the corresponding near or distancevision correction, respectively. In a conventional bifocal contact lensof the segmented or translating type, the lens is divided into twosomewhat D-shaped zones. Usually the upper area is for distance visioncorrection, whereas the lower area is for near vision correction. Suchconventional segmented contact lenses require some sort of movement ofthe lens relative to the eye to achieve acceptable visual acuity forboth distant and near vision.

One accepted method of fitting contact lenses is based on taking socalled K readings (which measure the center of the cornea) and fittingthe center of the contact lens in a predetermined relationship to thosereadings. This, however, is not the only method of fitting contactlenses.

In all conventional bifocal fitting techniques, the bifocal ormultifocal contact lenses is optimally designed to be particularlypositioned on the cornea. However, it is very difficult in many cases,to position the lens to achieve the required fit. In general, thehardest part of fitting a lens is to position the lens at a desiredlocation on the patient's cornea.

Precise fitting of a bifocal contact lens to the eye is crucial in socalled simultaneous vision contact lenses where the brain receives bothnear and far vision input and selects between the near vision input andthe far vision input, depending on the desired object(s) of perception.

As mentioned above, the segmented bifocal contact lenses translate tosome extent on the eye. Such lenses cannot be locked onto the cornea.However, for good vision, some stability is necessary.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a multifocal contactlens.

Another, more particular, object of the present invention is to providesuch a contact lens wherein the refractive power is defined by formingaspheric power curves on anterior and/or posterior surfaces of the lens.

Another particular object of the present invention is to provide such amultifocal contact lens which is made from a polymer material whichprovides at least about 10% by weight water after hydration.

Yet another object of the present invention is to provide such a lenswhich has at least one spheric or aspheric posterior surface, or acombination of spheric and aspheric surfaces.

These and other objects of the present invention may be gleaned from thedrawings and detailed descriptions set forth herein.

SUMMARY OF THE INVENTION

A multifocal contact lens customized for a patient has, in accordancewith the present invention, an anterior side with a power curve definedin part by a (i) central aspheric surface, (ii) an inner annular surfacecontiguous with the central aspheric surface, (iii) a second annularsurface contiguous along a radially inner periphery with the innerannular aspheric surface, and (iv) an outer annular surface contiguousalong a radially inner periphery with the second annular asphericsurface. Each of the annular surfaces is concentric or coaxial with thecentral aspheric surface. The central aspheric surface corresponds to adistance vision correction zone. The inner annular surface is anaspheric surface corresponding to a progressive add zone with a standardeccentricity between approximately -1.5 and approximately -5.0. Thesecond annular surface corresponds to a near vision correction zone, andthe outer annular surface corresponds to a distant vision correctionzone.

According to other features of the present invention, the centralaspheric surface has a diameter between approximately 1.5 mm andapproximately 2.5 mm, the inner annular surface has an outer diameterbetween approximately 2.0 mm and approximately 3.5 mm, the secondannular surface has an outer diameter between approximately 2.3 mm andapproximately 4.0 mm, and the outer annular surface has an outerdiameter between approximately 3.5 and approximately 8.0 mm. In onespecific embodiment of the invention, the central aspheric surface has adiameter of approximately 2.2 mm, the inner annular surface has an outerdiameter of approximately 2.8 mm, the second annular surface has anouter diameter of approximately 3.5 mm, and the outer annular surfacehas an outer diameter of approximately 8.0 mm.

According to a further feature of the present invention, the centralaspheric surface has a standard eccentricity between approximately -0.6and approximately -1.0. In the specific embodiment of the invention, thecentral aspheric surface has an eccentricity of approximately -0.8.

According to another feature of the present invention, the inner annularsurface has a standard eccentricity between approximately -3.0 andapproximately -5.0.

According to additional features of the present invention, the secondannular surface and the outer annular surface are both spheric. However,either or both of the second annular surface and the outer annularsurface may be aspheric.

The anterior side of the lens may have an annular lenticular area withan inner periphery contiguous with the outer annular surface and with anouter diameter between approximately 8.0 mm and approximately 14.5 mm.

In accordance with further features of the present invention, thecentral aspheric surface has a maximum change in power of approximately1/2 diopter from the center radially outwardly to the peripheral edge,while the inner annular surface has a maximum change in refractive powerof approximately three and one-half diopters as measured radially froman inner periphery of the inner annular surface to an outer peripherythereof.

It is contemplated that the multifocal contact lens has an asphericcornea-fitting posterior surface, with an eccentricity magnitude rangingfrom 0.0 to about 1.0.

A multifocal contact lens in accordance with the present invention maybe manufactured from hydrophilic or soft (hydrogel) polymeric materialsi.e., polymeric materials which contain at least about 10% by weightwater after hydration, such as disclosed in U.S. Pat. Nos. 5,314,960 and5,314,961, the disclosure of which is hereby incorporated by reference.

In accordance with a more general conceptualization of the presentinvention, a multifocal contact lens customized for a patient has ananterior side with a power curve defined in part by a (i) centralaspheric surface, (ii) an inner annular surface contiguous with thecentral aspheric surface, (iii) a second annular surface contiguousalong a radially inner periphery with the inner annular asphericsurface, and (iv) an outer annular surface contiguous along a radiallyinner periphery with the second annular aspheric surface. Each of theannular surfaces is concentric or coaxial with the central asphericsurface. The inner annular surface is an aspheric surface correspondingto a progressive add zone with a standard eccentricity having amagnitude between approximately 1.5 and approximately 5.0.

In a specific embodiment of the invention, the central aspheric surfacecorresponds to a distance vision correction zone, the progressive addzone corrects intermediate and near vision, the second annular surfacecorresponds to a near vision correction zone, and the outer annularsurface corresponds to a distant vision correction zone. In addition,the standard eccentricity of the inner annular surface is betweenapproximately -1.5 and approximately -5.0 and, more preferably, between-3.0 and -5.0.

In a similar bifocal contact lens in accordance with the presentinvention, the central aspheric surface corresponds to a near visioncorrection zone and has a standard eccentricity between approximately+1.5 and +5.0 and preferably between approximately +3.0 and +3.5,whereas the inner annular surface has a standard eccentricity betweenapproximately +1.5 and approximately +3.5 and preferably about +2.5. Thesecond annular correction surface has a standard eccentiricity betweenapproximately +0.3 and approximately +1.0 and preferably approximately0.8. In such a lens, the central aspheric correction zone has a diameterbetween about 1.1 mm and about 2.2 mm, while the inner annular surfacehas an outer diameter between about 1.1 mm and about 2.5 mm. The secondannular surface has an outer diameter between about 2.0 mm and about 8.0mm. Usually, a lens with a central near vision correction zone inaccordance with the present invention will have only three visioncorrection zones, although a fourth zone may be appropriate in somecases.

A customized multifocal contact lens in accordance with an even moregeneral conceptualization of the present invention has an anterior sidewith a power curve defined in part by a central aspheric surface and anannular surface contiguous and coaxial or concentric with the centralaspheric surface, the annular surface being an aspheric surfacecorresponding to a progressive add zone with a standard eccentricityhaving a magnitude between approximately 1.5 and approximately 5.0.Where the central aspheric surface corresponds to a distance visioncorrection zone, the annular surface is an aspheric surfacecorresponding to a progressive add zone with a standard eccentricitybetween approximately -1.5 and approximately -5.0. In that case, thecentral aspheric surface has a diameter between about 1.5 mm and 2.8 mm,while the annular surface has an outer diameter between about 1.5 mm and8.0 mm. Of course, the outer diameter of the annular surface is largerthan the outer diameter of the central aspheric surface.

The present invention relies in part on a method for preparing acustomized soft or hydrophilic multifocal contact lens wherein astandard diagnostic hydrophilic contact lens having a predeterminedrefractive power for distance vision is first placed on the patient'seye and allowed to seat itself in a natural position. The hydrophiliclens of the present invention will generally seat itself in asubstantially centered position (which term shall include a somewhatoff-centered position).

In one step of the method, an over-refraction is performed using thediagnostic lens in its natural position on the patient's cornea todetermine an aspheric power curve which may be applied to a firstportion or area of a prescription multifocal contact lens to provideoptimal distance vision for the patient. In another step, a furtherover-refraction is performed to determine a second aspheric curve toprovide near vision for the patient. As discussed above, the distancevision area may be a central area of the lens, while the near visionarea is an annular area concentric or coaxial with the central area andadjacent thereto. Alternatively, the central zone may be a near visioncorrection zone, while distance vision is corrected by an annular zonelocated concentrically or coaxially with respect to the central zone. Inboth cases, a further distance vision correction zone may be provided ina lenticular area of the lens. The refractive power of this additionalzone may be defined in part by a spheric surface on the anterior side ofthe lens conforming to the prescription needs of the individual patient.In any event, the outer distance vision correction zone is effective toassist in the correction of distance vision under low levels ofillumination, for example, during night driving.

The patient is fitted with a lens having the same posterior profile asthe diagnostic lens and an anterior profile with two or more concentricor coaxial aspheric surfaces having different respective eccentricityvalues which are standard values selectable from a plurality ofpredetermined eccentricities. The anterior power curve will generallycomprise at least two and may comprise as many as four aspheric curves,each having a different eccentricity value, to provide adequate visionfor near, intermediate and far distances. In certain instances, such asin mature presbyopes, in order to accommodate near, intermediate anddistance vision, the prescription lens preferably will comprise central,paracentral and peripheral aspheric curves, each having a differenteccentricity value and a clinically determined power or spheric basecurvature, on the anterior surface of the lens and a single posteriorspheric or aspheric curve of predetermined eccentricity, or optionallyand preferably, a spheric curve combined with an aspheric curve ofpredetermined eccentricity.

Upon placement of a diagnostic hydrophilic contact lens on the cornea ofa patient's eye so that the fitting surface is in substantial alignmentwith the cornea, the diagnostic lens usually aligns itself with thecornea in a substantially centered position. In this position, where thediagnostic lens has two aspheric power curves and one spheric powercurve, the patient may have adequate distance vision. With theappropriate diagnostic lens in place, the patient's near vision will bedetermined. Over-refraction of the lens for near vision will indicate aspheric or aspheric power curve to be cut on the anterior side of thislens. The lens which is produced from this process may be adequate toprovide intermediate vision, in addition to near and distance vision.

Generally, a diagnostic lens used in a fitting method in accordance withthe present invention will have a plurality of concentric or coaxialareas with respective predetermined power curves on the anterior side ofthe lens.

To accommodate a patient with a multifocal contact lens in accordancewith the present invention, the maximum change in refractive power in aradially outward direction across any distance vision correction zone(plan view) should be no greater than approximately one diopter. Thus,the change in refractive power from the center of the lens to theboundary between a central distant-vision correction zone and a firstannular correction zone (near vision) should be no greater thanapproximately one diopter and preferably no greater than one-halfdiopter. Similarly, the change in refractive power across the width ofan annular distance vision correction zone generally should be nogreater than approximately 1 diopter and preferably no greater thanone-half diopter. It is to be noted, additionally, that the change ineccentricity from one correction zone to the next should be gradual, toreduce stress on the eye. Thus, in certain instances two aspheric curvesmay suffice to provide adequate multifocal vision and in otherinstances, one or more additional aspheric surfaces of varyingeccentricity will be used to provide the gradual change between zones toaccommodate the patient's vision.

A method for use in preparing a customized multifocal contact lensutilizes, in accordance with a relatively particular conceptualizationof the present invention, a standard diagnostic contact lens having aconcave cornea-fitting posterior surface, the diagnostic contact lensalso having (i) a convex anterior surface with a central asphericsurface corresponding to a distant vision correction zone of apredetermined refractive power, (ii) an aspheric inner annular surfacecontiguous with the central aspheric surface and corresponding to aprogressive add zone with a standard eccentricity between approximately-1.5 and approximately -5.0, (v) a second annular surface contiguousalong a radially inner periphery with the inner annular asphericsurface, and (vi) an outer annular surface contiguous along a radiallyinner periphery with the second annular aspheric surface. Each of theannular surfaces is concentric or coaxial with the central asphericsurface. The second annular surface corresponds to a near visioncorrection zone of predetermined refractive power, while the outerannular surface corresponds to a distant vision correction zone ofpredetermined refractive power. The method includes the steps of (a)placing the diagnostic contact lens on the cornea of a patient's eye sothat the posterior surface is in substantial contact with the cornea,(b) allowing the diagnostic contact lens to align itself with the corneain a natural position while the patient looks at an effectively distantobject and (c) disposing a series of test lenses before the patient'seye, upon aligning of the diagnostic contact lens in the naturalposition, to determine a first aspheric power curve with which thecentral aspheric surface could be formed to provide optimal far visionfor the patient under conditions of relatively high illumination and tofurther determine a power curve with which the outer annular surfacecould be formed to provide optimal distance vision under conditions ofrelatively low illumination. In another step, while the patient looks atan effectively near object, another series of test lenses is disposedbefore the patient's eye to determine a power curve with which thesecond annular surface could be formed to provide optimal near visionfor the patient under conditions of average reading illumination.

The fitting or lens preparation method described above recognizes thedifficulty of providing adequate multifocal hydrophilic contact lenses.However, instead of struggling to achieve absolute corneal centering, assome fitting techniques attempt, the instant method obviates thedifficulty by assuming that the greatest majority of fitted multifocallenses will be centered or slightly off-centered on the cornea. In amethod in accordance with the present invention, the diagnostic lenspositions itself in its natural position, which, in hydrophilic lenses,is centered or substantially centered (slightly off-center). Because thefinished lens has the same back surface design as the diagnostic lens,there is no need to further position either the diagnostic lens or thefinished product, which should naturally position the same way as thediagnostic lens.

The present invention recognizes that each cornea is different and,instead of molding or fitting a lens precisely to center on the eye, theinstant contact lens preparation technique selects among a fixed numberof prescribed standard fitting or diagnostic lenses and then modifiesonly the anterior surface in order to achieve an optimal multifocalvision. This method can change differential powers of the two or moreconcentric or coaxial anterior aspheric zones without appreciablyaffecting the fit.

Because the anterior surface of the lens manufactured in accordance withthe present invention contains multiple concentric or coaxial asphericsurfaces, the lens has a multiplicity of refractive powers. For acentrally located aspheric surface which corrects for distance vision,these powers are least plus or most minus at the vertex andprogressively become more plus or less minus from the vertex radially tothe periphery of the central zone. For a central near vision correctionzone, these powers are most plus or least minus at the vertex andprogressively become less plus or more minus from the vertex radially tothe periphery of the central zone.

Whenever one refracts over such a lens on the eye using sphericophthalmic lenses, the patient subjectively chooses that ophthalmic lenspower combined with the multiplicity of lens powers in the asphericcentral zone of the contact lens which provides the best acuity ofvision at both far distance and near distance. There is a corticalinterpretation of the independent images to determine the bestacceptable summation of images.

The present invention may be used with all standard contact lensmaterials, i.e. rigid (gas permeable or PMMA), but is preferably usedwith soft (hydrogel) polymeric materials i.e., polymeric materials whichcontain at least about 10% by weight water after hydration, such asdisclosed in U.S. Pat. Nos. 5,314,960 and 5,314,961.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic front elevational view of a diagnostic contactlens for use in fitting a patient with a simultaneous type multifocalcontact lens in accordance with the present invention.

FIG. 2 is a cross-sectional view taken along line II--II in FIG. 1,showing in phantom lines an ophthalmic lens positioned in front of thediagnostic lens for fitting purposes.

FIG. 3 is a partial cross-sectional view, on an enlarged scale, of theophthalmic lens of FIG. 2, showing an edge bevel.

FIG. 4 is a schematic cross-sectional view of a multifocal contact lens.

FIG. 5 is a schematic cross-sectional view of a multifocal contact lensin accordance with the present invention.

FIG. 6 is a schematic front elevational view, on an enlarged scale, ofanother multifocal contact lens.

FIG. 7 is a schematic front elevational view, on an enlarged scale, of amultifocal contact lens in accordance with the present invention.

DETAILED DESCRIPTION

In preparing a customized multifocal contact lens, a standard diagnosticcontact lens 10 as illustrated in FIGS. 1 and 2 is first placed on thepatient's eye and allowed to seat itself in a natural, substantiallycentered, position. The anterior side of the lens has a plurality ofconcentric or coaxial aspheric surfaces essentially alignable with thecornea of the patient's eye. The posterior side of the lens is formedwith a spheric or aspheric surface which is adapted to fit the lens tothe cornea of the patient. If, upon placement on the patient's cornea,the diagnostic lens does not produce adequate distance vision, a firstover-refraction is performed to determine a first aspheric power curvefor a central anterior zone of the lens. This central power curve isresponsible for correcting distance vision and is provided by modifyinga central portion of the anterior surface of a finished prescriptionlens having the same posterior surface as the diagnostic lens 10. Anadditional over-refraction is then performed to determine a second powercurve for an annular anterior area or zone of the lens to provideadequate near distance correction. The second power curve is formed bymodifying an annular portion of the anterior surface of the finishedprescription lens. A third, spheric, power curve is provided in anannular, outer or lenticular area of the finished lens to assist in thecorrection of distance vision under low levels of illumination, forexample, during night driving. Generally, an anterior surface of thelens will have only two anterior annular aspheric power curves. In othercases, the anterior surface may have more than two aspheric powercurves.

As described in detail hereinafter, if the above discussed procedurefails to provide satisfactory near and distance vision, a differentdiagnostic lens may be used to determine aspheric power curves where thecentral zone on the anterior side of the lens is a near visioncorrection zone, while a first annular area is a distance visioncorrection zone.

As shown in FIGS. 1 and 2, a first diagnostic lens 10 tried on thepatient has a concave cornea-fitting posterior surface 14. Surface 14may be spheric or preferably, aspheric with a predetermined eccentricityranging from 0.0 to about 1.0. Lens 10 also has, on an anterior side, astandard annular spheric or aspheric surface 12 and a standard centralaspheric surface 18, each surface having a predetermined eccentricity.Generally, surfaces 12 and 18 have different eccentricities. However, itis also possible for them to have the same eccentricity. In addition,this first diagnostic lens may have, at an annular periphery of lens 10,an edge radius 22 (FIGS. 2 and 3) which is turned to the side of acenter line CN. Accordingly, by virtue of the use of an asphericsurface, surface 14 of the lens is curved down to fit against the corneaof the patient's eye. It is noted that the edge radius is an optionalfeature of the lens.

In fitting a patient with a multifocal contact lens, diagnostic lens 10is placed on the cornea of the patient's eye so that cornea-fittingposterior surface 14 is in substantial contact with the cornea. Lens 10is allowed to align itself with the cornea in a substantially centeredposition. Upon an alignment of diagnostic contact lens 10 in thesubstantially centered position, a series of conventional sphericopthalmic test lenses 26 (FIG. 2) are disposed before the lens 10 on thepatient's eye to determine a power curve 28 (FIG. 2) with which anteriorsurface 18 of a central lens portion 16 can be formed to provide optimaldistance vision for the patient. A subsequent over-refraction isperformed to determine a spheric or aspheric power curve with whichannular surface 12 of the lens may be formed to provide optimal nearvision for the patient.

To optimize the fitting of lens 10 to any particular patient's cornea,lens 10 is first selected from a kit of standard diagnostic contactlenses each having concave cornea-fitting posterior surface 14 andcentral lens portion 16 with predetermined annular spheric or asphericsurface 12 and predetermined central aspheric surface 18. Surface 18 hasa predetermined standard eccentricity between approximately 0.40 andapproximately 1.80 and preferably between approximately 0.6 and 1.0.

Most of the lenses 10 in the kit have cornea-fitting posterior surfaces14 which are spheric or aspheric with eccentricities between 0.0 andabout 1.0.

The patient is fitted first with a diagnostic or fitting contact lens 10having a posterior surface 14 which substantially matches the cornea ofthe patient about the iris. Of course, precise matching is undesirable,because space is required for tear flow, etc.

Two or more different standard diagnostic contact lenses 10 may betested sequentially on the cornea of the patient to determine which hasthe most appropriate cornea-fitting surface 14 and anterior surfaces 12and 18. However, a suitable diagnostic lens may be preselected inasmuchas appropriateness of surfaces 12 and 18 depends in large part on theneeds of the particular patient, for example, on whether the lens is tobe used primarily for reading, primarily in social situations, orprimarily for distance vision correction.

Upon the selection of a diagnostic lens 10 which has a suitablecornea-fitting surface 14 and which provides the best distance vision, afirst over-refraction is performed, if necessary, to determine anaspheric power curve 28 with which the central area 18 of the lens isformed to optimize the correction for distance vision. The sameover-refraction procedure may be used to determine a spheric power curvewith which an annular lenticular or outer area of the lens may be formedto provide further distance vision correction.

A second over-refraction procedure is subsequently performed todetermine a power curve for modifying annular spheric or asphericsurface 12 of central portion 16 for the final lens to provide adequatenear vision. This over-refraction procedure is performed with thepatient focusing on a near object. Upon the determination of anappropriate near vision power curve, the appropriate spheric or asphericcurve is formed on the anterior side of a prescription lens having thesame posterior configuration as the diagnostic lens. This lens, oncemanufactured to the prescription established by the diagnostic procedureshould provide adequate near, distance and intermediate vision. However,as discussed below with reference to FIG. 7, intermediate vision may becorrected by a paracentral aspheric progressive-add surface on theanterior side of the lens.

Generally, as illustrated in FIG. 5, a multifocal contact lens 110customized for a patient pursuant to the abovedescribed fittingmethodology will have an anterior side 112 with a power curve defined inpart by a central aspheric surface 114 and at least one annular asphericsurface 116 concentric or coaxial therewith. Where central asphericsurface 114 corresponds to a distance vision correction zone, it willhave a standard eccentricity value between about -0.6 and about -1.2and, more preferably, between about -0.75 and about -0.85. In lens 110,annular aspheric surface 116 corresponds to a progressive-add correctionzone and has a standard eccentricity value between about -1.35 and about-2.5. The negative eccentricities mean that the deviations from sphericresult in a radius of curvature which is smaller than, or reduced withrespect to, a spheric radius. Conversely, where eccentricities arepositive, the deviations from spheric result in a radius of curvaturewhich is greater than, or increased with respect to, a spheric radius.Negative eccentricities thus correspond to a steepening of the powercurve while positive eccentricities correspond to a flattening of thepower curve.

As further illustrated in FIG. 5, anterior side 112 of lens 110 also hasan annular lenticular area 118 with a spheric power surface providing anadditional correction for distance vision. The power curve forlenticular area 118 is determined during the same over-refractionprocedure used to determine the power curve for central aspheric surface114.

Patient-customized lens 110 has a cornea-fitting posterior surface 120which is either spheric or aspheric with an eccentricity value rangingfrom 0.0 to about 1.0. As discussed above, this posterior surface 120has essentially the same form or profile as posterior surface 14 of thediagnostic lens 10 used to determine the power curves for surfaces 114,116, and 118.

Preferably, central aspheric surface 114 has a diameter d1 betweenapproximately 1.6 mm and approximately 2.3 mm, while annular asphericsurface 116 has a diameter d2 between approximately 2.9 mm and 3.6 mm.For example, central aspheric surface 114 may have a standard diameterof approximately 2.2 mm, while annular aspheric surface 116 has astandard diameter of approximately 3.0 mm or 3.5 mm. In some cases, thediameter of central aspheric surface 114 will be reduced toapproximately 1.9 mm, for purposes of providing adequate visionenhancement.

Lens 110 may be manufactured from a hydrophilic polymer such as thosedisclosed in U.S. Pat. Nos. 5,314,960 and 5,314,961, the disclosures ofwhich are hereby incorporated by reference.

As discussed above, in some cases, depending on the patient's reactionto the over-refraction procedure, central aspheric surface 114 ofcustomized multifocal contact lens 110 corresponds to a near visioncorrection zone and has a standard eccentricity value between about 1.35and about 2.5. Concomitantly, annular aspheric surface 116 correspondsto a distance vision correction zone having a standard eccentricityvalue between about 0.6 and about 1.2 and, preferably, between about 0.8and about 0.9. In this embodiment also, annular lenticular area 112 isprovided with a spheric power surface providing a distance visioncorrection.

It is to be noted that one eye of a patient may be provided with a lens110 where central aspheric surface 114 is a distance vision correctionzone, while the other eye of the patient is provided with a lens 110where central aspheric surface 114 is a near vision correction zone.This is a kind of modified monovision, based on the same principles asthose underlying the contact lens combinations disclosed in U.S. Pat.Nos. 5,002,382 or 5,024,517. Alternatively, where the central asphericsurfaces 114 of both contact lenses 110 correct distance vision and havestandard eccentricity values between about -0.6 and about -1.2 and theannular aspheric surfaces correspond to progressive-add-type correctionzones with standard eccentricity values between about -1.35 and about-2.5, the central aspheric surface of the lens for a dominant eye of thepatient is larger in diameter than the central aspheric surface of thelens for a nondominant eye of the patient. In this case, the diameter ofannular aspheric surface 114 of the dominant lens is substantially equalto the diameter of the annular aspheric surface of the nondominant lens.Specifically, the diameter of the central aspheric surface of thedominant lens is about 2.2 mm and the diameter of the central asphericsurface of the nondominant lens is about 1.9 mm, while the diameter ofthe annular aspheric surface of either lens is between about 3.0 mm andabout 3.5 mm.

As illustrated in FIG. 6, another customized multifocal contact lens 122has an anterior side 124 with a power curve defined in part by a centralaspheric surface 126 and two annular aspheric surfaces 128 and 130concentric or coaxial therewith. Central aspheric surface 126corresponds to an intermediate vision correction zone and has a standardeccentricity value between about 1.2 and about 1.7, while annularaspheric surface 128 corresponds to a distance vision correction zonewith a standard eccentricity value between about 0.6 and about 1.2.Annular aspheric surface or lenticular area 130 corresponds to a nearvision correction zone with a spheric power curve. Central asphericsurface 126 has a diameter d3 between approximately 1.5 mm and 2.0 mm,while annular aspheric surface 128 has a diameter d4 betweenapproximately 3.0 mm and 3.7 mm. Again, lens 122 has a posterior profileor surface (not shown) which is the same as that of the diagnostic lensultimately selected for determination of the powers of aspheric surfaces126, 128, 130 during the over-refraction process. The eccentricity ofthe posterior surface, as well as the eccentricities of surfaces 126,128, and 130, are standard values selectable from a plurality ofpredetermined eccentricities. Lens 122 is particularly well suited formature presbyopes, in order to accommodate near, intermediate anddistance vision.

To provide adequate vision correction without confusing visualperception of the patient, the maximum change in refractive power in aradially outward direction across any single distance vision correctionzone (plan view) 114, 116, 118 (FIG. 5) or 128 (FIG. 6) should be nogreater than approximately one diopter or, more preferably, one-halfdiopter. Thus, the change in refractive power from the center of a"center distance" lens 110 to the boundary between centraldistant-vision correction zone 114 and annular near vision correctionzone 116 should be no greater than approximately one diopter or, morepreferably, one-half diopter. Similarly, the change in refractive poweracross the width of annular distance vision correction zone 116 of a"center near" lens generally should be no greater than approximately 1diopter or, more preferably, one-half diopter. In addition, the changein eccentricity from one correction zone to the next should be gradual,to reduce stress on the eye. Thus, in certain instances two asphericcurves may suffice to provide adequate multifocal vision and in otherinstances, one or more additional aspheric surfaces of varyingeccentricity will be used to provide the gradual change between zones toaccommodate the patient's vision.

In order to secure acceptable distance vision and near vision in amulti-focal contact lens pursuant to the abovedescribed procedure,particularly where there is a significant difference in "add" betweenthe prescription or power curve for distance vision and the prescriptionor power curve for near vision, the lens may be formed to float ortranslate slightly on the cornea to an extent greater than normal. Thus,in the case of a contact lens having two anterior aspheric surfaces, asteeper part of the power curve may be shifted over the pupil for nearvision. In the case of a lens with a third, paracentral anterioraspheric surface, the slight translation of the lens may serve to shiftthe lenticular area more squarely over the pupil for near vision.

As depicted in FIG. 7, a multifocal contact lens 200 customized for apatient has an anterior side with a power curve defined in part by acentral aspheric surface 202, an inner annular surface 204 contiguouswith central aspheric surface 202, a second annular surface 206contiguous along a radially inner periphery 208 with inner annularaspheric surface 204, and an outer annular surface 210 contiguous alonga radially inner periphery 212 with second annular aspheric surface 206.Each of the annular surfaces 204, 206, and 210 is concentric or coaxialwith central aspheric surface 202. Central aspheric surface 202corresponds to a distant vision correction zone. Inner annular surface204 is an aspheric surface corresponding to a progressive add zone witha standard eccentricity between approximately -1.5 and approximately-5.0 and, more preferably between approximately -3.0 and approximately-5.0. Second annular surface 206 corresponds to a near vision correctionzone, while outer annular surface 210 corresponds to a distant visioncorrection zone. Annular surfaces 206 and 210 may be spheric oraspheric.

Central aspheric surface 202 has a diameter d1' between approximately1.5 mm and approximately 2.5 mm, while inner annular surface 204 has anouter diameter d2' between approximately 2.0 mm and approximately 3.5mm. Second annular surface 206 has an outer diameter d3' betweenapproximately 2.3 mm and approximately 4.0 mm, and outer annular surface210 has an outer diameter d4' between approximately 3.5 andapproximately 8.0 mm. An annular lenticular area 214 of lens 200 has nopower curve and has an outer diameter d5' between approximately 8.0 mmand approximately 14.5 mm. Central aspheric surface 202 has a standardeccentricity between approximately -0.6 and approximately -1.0 and morepreferably between about -0.75 and about -0.85.

In one specific embodiment of the invention, diameters d1' through d5'are approximately 2.2 mm, approximately 2.8 mm, approximately 3.5 mm,approximately 8.0 mm, and approximately 14.5 mm, respectively. Centralaspheric surface 202 has an eccentricity of approximately -0.8, whileinner annular surface 204 has a standard eccentricity of approximately-5.0.

Central aspheric surface 202 has a maximum change in power ofapproximately 1/2 diopter from the center radially outwardly to itsperipheral edge 216, while inner annular, progressive-add surface 204has a maximum change in refractive power of approximately three andone-half diopters as measured radially from edge 216 to periphery 208.

Multifocal contact lens 200 has an aspheric cornea-fitting posteriorsurface (not designated), with an eccentricity magnitude ranging from0.0 to about 1.0.

Multifocal contact lens 200 may be manufactured from hydrophilic or soft(hydrogel) polymeric materials i.e., polymeric materials which containat least about 10% by weight water after hydration, such as disclosed inU.S. Pat. Nos. 5,314,960 and 5,314,961, the disclosure of which ishereby incorporated by reference.

Central aspheric surface 202 corrects distance vision particularly underconditions of high illumination, while outer annular surface 210corrects distance vision particularly under conditions of lowillumination such as night driving. Progressive-add surface 204 correctsvision for intermediate distances.

Lens 200 is fitted as described above, using a diagnostic or test lenswith the same posterior surface as lens 200 and an anterior side with acentral aspheric surface of a predetermined standard eccentricity andpower and at least one annular spheric or aspheric surface of apredetermined standard eccentricity and power. Power curves for centralaspheric surface 202 and outer annular surface 210 are determined, asdiscussed above, during a first over-refraction procedure wherein adiagnostic or test lens is placed on the cornea of the patient's eye. Apower curve for second annular surface 206 is determined during a secondover-refraction procedure. The power curves for central aspheric surface202 and outer annular surface 210 may be determined under highillumination and low illumination levels, respectively. The power curvefor paracentral or progressive-add surface 204 is determined by thepreselected standard eccentricity of that intermediate zone and by theresults of the first (distant vision) over-refraction procedure. Anyprogressive add zone (eccentricity of high magnitude) will provide acontinuous range of powers to the retina and the brain of the patient.The patient's visual cortex selects from among that continuous range ofpowers or adds to obtain a focused sight.

It is to be noted that in some circumstances, the outer two annularsurfaces or correction zones 206 and 210 may be omitted in aprescription lens. Such a simplified lens has only a central asphericsurface 202 and an annular progressive add surface or zone. The centralaspheric surface has a diameter between about 1.5 mm and about 2.8 mm,while the annular progressive add zone has an outer diameter betweenabout 1.5 mm and about 8.0 mm the outer diameter of the annularprogressive add zone being larger than the outer diameter of the centralaspheric surface. The progressive add zone has a standard eccentricityhaving a magnitude between approximately 1.5 and approximately 5.0.Where the central aspheric surface corresponds to a distance visioncorrection zone, the annular surface is an aspheric surfacecorresponding to a progressive add zone with a standard eccentricitybetween approximately -1.5 and approximately -5.0.

In another modification of the contact lens of FIG. 7, only the outerannular zone 210 is omitted.

In an alternative lens having the general structure set forth above withrespect to FIG. 7, the central aspheric surface corresponds to a nearvision correction zone with a standard eccentricity betweenapproximately +1.5 and approximately +5.0 and preferably betweenapproximately +3.0 and approximately +3.5, whereas the inner annularsurface has a standard eccentricity between approximately +1.5 andapproximately +3.5 and preferably about +2.5. The second annularcorrection surface has a standard eccentricity between approximately+0.3 and approximately +1.0 and preferably approximately 0.8. In such alens, the central aspheric correction zone has a diameter between about1.1 mm and about 2.2 mm, while the inner annular surface has an outerdiameter between about 1.1 mm and about 2.5 mm. The second annularsurface has an outer diameter between about 2.0 mm and 8.0 mm. Usually,a lens with a central near vision correction zone in accordance with thepresent invention will have only three vision correction zones, althougha fourth zone may be appropriate in some cases.

As illustrated in FIGS. 1 and 2, diagnostic lens 10 has at least onetransition junction 24 where the anterior annular aspheric surface 12meets central aspheric surface 18. At transition junction 24, the radiiof curvature of surfaces 12 and 18 are approximately equal. However, theeccentricities of those aspheric anterior surfaces remain different.

An eccentricity between 0.0 and about 1.0 for cornea-fitting posteriorsurface 14 of a diagnostic hydrophilic lens or a finished prescriptionlens is in accordance with the aspheric topographical characteristics ofthe human cornea. With such an eccentricity, cornea-fitting posteriorsurface 14 is fitted relatively tightly to the patient's eye, so thatthe lens, which may move slightly with eye and eyelid movement, does notmove significantly with movement of the upper eyelid.

Upon the completion of the over-refraction process, the patient isfitted with a prescription lens 110, 122, 200 (generally, from a lensproduction laboratory) which is substantially identical to the finallyused diagnostic lens 10. The prescription lens may have two anterioraspheric surfaces or three (or more) anterior aspheric surfaces (FIGS. 5or 7). The anterior surface of the selected lens blank is machined or,more specifically, lathed to produce the appropriate anterior asphericsurfaces 126, 128, 130 (FIG. 6) or 202, 204, 206, 210 (FIG. 7).Alternatively, either the posterior or anterior surface of the lens orthe entire lens, including posterior and anterior surfaces, may bemolded.

In most cases, over-refraction of diagnostic lens 10 will provideadequate vision for near, intermediate and far distances. In such acase, a lens having a posterior surface with a single spheric oraspheric curve 14 may be used with good success. In certain instances,it may be advantageous to provide a second aspheric surface (not shown)on the periphery of the cornea-fitting posterior surface 14, each of theaspheric posterior surfaces ranging in eccentricity from about 0.0 toabout 1.0.

By incorporating the features of the contact lenses, it is now possibleto avoid having to fit the patient in a rigid set or establishedposition, thus obviating one of the more difficult problems ofbifocal/multifocal contact lens fitting. Instead, the fit or position ofthe lens is first established naturally and thereafter, the visualcharacteristics of the lens are designed into the finished lens.

Generally, as is well known in the art, if the anterior power curve isdecreased by 12 lines for each diopter, the add is 1.0. A decrease of 6lines for each 1/2 diopter results in an add of 0.5, while a decrease of24 lines for each 2 diopters results in an add of 2.0. Similarly, adecrease of 48 lines for each 4 diopters results in an add of 4.0. Thisrule of thumb is helpful in guiding the practitioner to design a lenswhich can accommodate varying powers of the lens in predetermineddistances for maximum fit and visual effectiveness.

FIG. 4 shows a special multifocal hydrophilic contact lens 50 with anoptional enhanced intermediate vision correction. As illustrated in FIG.4, a multifocal hydrophilic contact lens 50 has an anterior surface orside 52 with three concentric or coaxial aspheric surfaces 54, 56, and58 each formed with a respective power curve having a standardeccentricity value between about 0.4 and about 2.5. The eccentricityvalues differ from one another by at least about 0.2 and by no more thanabout 0.8. Lens 50 has a concave cornea-fitting posterior surface 62which includes at least one aspheric surface having an eccentricityvalue between about 0.0 and about 1.0.

Hydrophilic multifocal soft lens 50 may include one or more spheric oraspheric posterior surfaces, but preferably, lens 50 has one asphericsurface 62 ranging in eccentricity from about 0.0 to about 1.0. Incertain embodiments of a contact lens, the posterior cornea-fittingsurface of the contact lens may have two annular aspheric surfaces, eachof which has an eccentricity value ranging from about 0.0 and about 1.0.

Central aspheric surface or power curve 54 provides distance vision andhas an eccentricity value with a smaller magnitude than the magnitude ofthe eccentricity value of paracentral aspheric surface or power curve 56which provides intermediate vision. The eccentricity of para-centralaspheric surface or power curve 56 in turn has a magnitude which issmaller than the magnitude of the eccentricity of peripheral asphericsurface or power curve 58, which provides a correction for near vision.Preferably, the eccentricity value of central aspheric power curve 54 isbetween about -0.4 and about -0.8, the eccentricity value ofpara-central aspheric surface or power curve 56 is between about -0.6and about -0.8, and the eccentricity value of peripheral asphericsurface or power curve 58 is between about -0.8 and about -1.2.

Aspheric surfaces or power curves 54, 56 and 58 are determined in afitting method utilizing a diagnostic lens having the same posteriorsurface 62 as lens 50 and an anterior surface 64 having a predeterminedstandard refractive power. That refractive power is for distance vision.Alternatively, the diagnostic lens may have a plurality of concentric orcoaxial areas with respective predetermined standard refractive powers,e.g., for distance vision and near vision, respectively. The diagnosticlens is selected from a kit of diagnostic lenses with differentposterior surfaces 62 and different overall dimensions. The diagnosticlens is selected to conform to the particular shape and dimensions of apatient's cornea.

The diagnostic contact lens is placed on the cornea of a patient's eyeso that posterior cornea-fitting surface 62 is in substantial contactwith the cornea. The diagnostic contact lens is allowed to align itselfwith the cornea in a substantially centered position while the patientlooks at an effectively distant object. Upon aligning of the diagnosticcontact lens in the substantially centered position, a series of testlenses is disposed before the patient's eye in a first over-refractionprocedure to determine central aspheric surface or power curve 54 forproviding optimal distance vision for the patient. In anotherover-refraction step, while the patient looks at an effectively nearobject, another series of test lenses is disposed before the patient'seye to determine aspheric surface or power curve 58 for providingoptimal near vision for the patient. In yet another over-refractionstep, while the patient looks at an intermediately distanced object, afurther series of test lenses is disposed before the patient's eye todetermine aspheric surface or power curve 56 for providing optimalintermediate distance vision for the patient.

Anterior aspheric surfaces or power curves 54, 56, and 58 are located ina central correction zone 66, an intermediate annular correction zone68, and a peripheral annular correction zone 70, respectively. Asphericsurfaces or power curves 54, 56, and 58 are concentric or coaxial with alens axis 72. It is to be noted that the eccentricity values of surfacesor power curves 54, 56, and 58 differ from one another by no more thanabout 0.8 in order to provide a smooth transition from one correctionzone 66, 68, or 70 to another.

A hydrophilic multifocal contact lens as depicted in FIG. 4 may haveonly a central correction zone 66 and a peripheral correction zone 70with associated aspheric surfaces or power curves 54 and 58 forcorrecting distance vision and near vision, respectively. Alternatively,four aspheric surfaces or power curves may be provided, all ranging ineccentricity from about 0.4 to about 1.8, preferably from about 0.6 toabout 1.0, each of the aspheric surfaces differing in eccentricity valuewithin the range of about 0.2 to about 0.8.

It is to be noted that the change in eccentricity from aspheric surfaceor power curve 54 to aspheric surface or power curve 56, as well as thechange in eccentricity from aspheric surface or power curve 56 toaspheric surface or power curve 58, should be gradual, to reduce stresson the eye.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are profferred by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A multifocal contact lens customized for apatient, having an anterior side with a power curve defined in part by a(i) central aspheric surface, (ii) an aspheric inner annular surfacecontiguous with said central aspheric surface, (iii) a second annularsurface contiguous along a radially inner periphery with said asphericinner annular surface, and (iv) an outer annular surface contiguousalong a radially inner periphery with said second annular surface, eachof the annular surfaces being concentric or coaxial with said centralaspheric surface, said central aspheric surface corresponding to adistance vision correction zone, said aspheric inner annular surfacecorresponding to a progressive add zone with a standard eccentricitybetween approximately -1.5 and approximately -5.0, said second annularsurface corresponding to a near vision correction zone, and said outerannular surface corresponding to a distant vision correction zone. 2.The lens defined in claim 1 wherein said central aspheric surface has adiameter between approximately 1.5 mm and approximately 2.5 mm, saidaspheric inner annular surface has an outer diameter betweenapproximately 2.0 mm and approximately 3.5 mm, said second annularsurface has an outer diameter between approximately 2.3 mm andapproximately 4.0 mm, and said outer annular surface has an outerdiameter between approximately 3.5 and approximately 8.0 mm.
 3. The lensdefined in claim 2 wherein said central aspheric surface has a diameterof approximately 2.2 mm, said aspheric inner annular surface has anouter diameter of approximately 2.8 mm, said second annular surface hasan outer diameter of approximately 3.5 mm, and said outer annularsurface has an outer diameter of approximately 8.0 mm.
 4. The lensdefined in claim 3 wherein said central aspheric surface has a standardeccentricity between approximately -0.6 and approximately -1.0.
 5. Thelens defined in claim 4 wherein said central aspheric surface has aneccentricity of approximately -0.8.
 6. The lens defined in claim 5wherein said aspheric inner annular surface has a standard eccentricitybetween approximately -1.5 and approximately -4.0.
 7. The lens definedin claim 6 wherein said second annular surface and said outer annularsurface are both spheric.
 8. The lens defined in claim 7 wherein saidanterior side has an annular lenticular area with an inner peripherycontiguous with said outer annular surface and with an outer diameterbetween approximately 8.0 mm and approximately 14.5 mm.
 9. The lensdefined in claim 8 wherein said central aspheric surface has a centerand a substantially circular peripheral edge, said central asphericsurface having a maximum change in power of approximately 1/2 diopterfrom said center radially outwardly to said peripheral edge.
 10. Thelens defined in claim 9, further comprising an aspheric cornea-fittingposterior surface.
 11. The lens defined in claim 10 wherein saidposterior surface has an eccentricity magnitude ranging from 0.0 toabout 1.0.
 12. The lens defined in claim 11 manufactured from ahydrophilic polymer.
 13. The lens defined in claim 1 wherein saidcentral aspheric surface has a standard eccentricity betweenapproximately -0.6 and approximately -1.0 and said aspheric innerannular surface has a standard eccentricity between approximately -1.5and approximately -4.0.
 14. The lens defined in claim 13 wherein saidcentral aspheric surface has an eccentricity of approximately -0.8. 15.The lens defined in claim 1 wherein said anterior side has an annularlenticular area with an inner periphery contiguous with said outerannular surface.
 16. The lens defined in claim 1 wherein said secondannular surface and said outer annular surface are both spheric.
 17. Thelens defined in claim 1 wherein said central aspheric surface has acenter and a substantially circular peripheral edge, said centralaspheric surface having a maximum change in power of approximately 1/2diopter from said center radially outwardly to said peripheral edge. 18.The lens defined in claim 1, further comprising an asphericcornea-fitting posterior surface having an eccentricity magnituderanging from 0.0 to about 1.0.
 19. The lens defined in claim 1manufactured from a hydrophilic polymer.
 20. The lens defined in claim 1wherein said aspheric inner annular surface has a maximum change inrefractive power of approximately three and one-half diopters asmeasured radially from an inner periphery of said aspheric inner annularsurface to an outer periphery thereof.
 21. A multifocal contact lenscustomized for a patient, having an anterior side with a power curvedefined in part by a (i) central aspheric surface, (ii) an asphericinner annular surface contiguous with said central aspheric surface,(iii) a second annular surface contiguous along a radially innerperiphery with said aspheric inner annular surface, and (iv) an outerannular surface contiguous along a radially inner periphery with saidsecond annular surface, each of the annular surfaces being concentric orcoaxial with said central aspheric surface, said aspheric inner annularsurface corresponding to a progressive add zone with a standardeccentricity having a magnitude between approximately 1.5 andapproximately 5.0, said central aspheric surface having an eccentricitywith a magnitude of at least approximately 0.6.
 22. The lens defined inclaim 21 wherein said central aspheric surface corresponds to a distancevision correction zone, said second annular surface corresponds to anear vision correction zone, and said outer annular surface correspondsto a distant vision correction zone, the standard eccentricity of saidaspheric inner annular surface being between approximately -1.5 andapproximately -5.0, said inner annular surface having a standardeccentricity between approximately -1.5 and approximately -4.0.
 23. Thelens defined in claim 21 wherein said central aspheric surface has astandard eccentricity with a magnitude between approximately 0.6 andapproximately 1.0.
 24. The lens defined in claim 23 wherein said centralaspheric surface corresponds to a distant vision correction zone and hasa standard eccentricity between approximately -0.6 and approximately-1.0.
 25. The lens defined in claim 21 wherein said anterior side has anannular lenticular area with an inner periphery contiguous with saidouter annular surface.
 26. A multifocal contact lens customized for apatient, having an anterior side with a power curve defined in part by acentral aspheric surface and an annular surface contiguous and coaxialor concentric with said central aspheric surface, said annular surfacebeing an aspheric surface corresponding to a progressive add zone with astandard eccentricity having a magnitude between approximately 1.5 andapproximately 5.0, said central aspheric surface having an eccentricitywith a magnitude of at least approximately 0.6.
 27. The lens defined inclaim 26 wherein said central aspheric surface corresponds to a distancevision correction zone, said annular surface being an aspheric surfacecorresponding to a progressive add zone with a standard eccentricitybetween approximately -1.5 and approximately -5.0.
 28. The lens definedin claim 27 wherein said central aspheric surface has a diameter betweenabout 1.5 mm and 2.8 mm, said annular surface having an outer diameterbetween about 1.5 mm and 8.0 mm, the outer diameter of said annularsurface being larger than the outer diameter of said central asphericsurface.
 29. The lens defined in claim 27 wherein said annular surfaceis an inner annular surface on said anterior side, said anterior sidealso having a second annular surface contiguous along a radially innerperiphery with said inner annular surface, said second annular surfacecorresponding to a near vision correction zone, said anterior side alsohaving an outer annular surface contiguous along a radially innerperiphery with said second annular surface, said outer annular surfacecorresponding to a distant vision correction zone.
 30. A multifocalcontact lens customized for a patient, having an anterior side with apower curve defined in part by a (i) central aspheric surface, (ii) aninner annular surface contiguous with said central aspheric surface, and(iii) a second annular surface contiguous along a radially innerperiphery with said inner annular surface, each of the annular surfacesbeing concentric or coaxial with said central aspheric surface, saidcentral aspheric surface corresponding to a near vision correction zonewith a standard eccentricity between approximately +1.5 andapproximately +5.0.
 31. The lens defined in claim 30 wherein said innerannular surface is an aspheric surface with a standard eccentricitybetween approximately +1.5 and approximately +3.5, said second annularsurface being an aspheric surface with a standard eccentricity betweenapproximately +0.3 and approximately +1.0.
 32. The lens defined in claim31 wherein said central aspheric surface has a standard eccentricitybetween approximately +3.0 and +5.0, said inner annular surface has astandard eccentricity of approximately 2.5, and said second annularsurface has a standard eccentricity of approximately +0.8.